This invention relates to over-rotation preventing devices for internal combustion engines and more particularly to a device for delaying the operation of a thyristor controlling the feed of an electric current to an ignition coil with a C.R. (capacitor-resistance) time constant circuit to thereby delay the ignition timing of an internal combustion engine.
There has been already provided a device for preventing the over-rotation of internal combustion engines with a governor mechanism. However, such governor mechanism rotates integrally with a crank shaft, operates to extend and contract and therefore has problems in that it requires a large mounting space, has a difficult to fit and is short mechanical life. On the other hand, there have been provided various electrical control circuits made to delay the timing of an ignition circuit. However, they are limited in the angle delaying method, can not positively prevent the over-rotation of internal combustion engines and have problems in that electric noises from these over-rotation preventing circuit influence the ignition circuit and disturb the normal ignition timing.